Weaving devices, commonly called looms, are known in the art and have been in existence in one or another form for thousands of years. Weaving devices are generally used for producing woven fabric. Generally speaking, weaving devices consist of a frame, a generally horizontal array of eyelets movably supported by the frame between an upper position and a lower position, and a mechanism for moving the eyelets between the two positions.
To set up a typical weaving device for operation, a thread, or any type of weavable strand, is drawn off a spool and passed through an eyelet of the weaving device, then passed through a guide which is on the opposite side of the eyelet from the spool. The guide may be in the form of a long horizontal slot, or a gap between to horizontal, vertically opposed rollers. Each eyelet is threaded in this manner with an individual thread.
Selected eyelets are oriented the upper position and slightly above the guide, while the remaining eyelets are oriented in the lower position and slightly below the guide. This difference in the relative positions of the eyelets with respect to each other and to the guide, causes the threads to form an upper and lower row of parallel threads. The upper row passes from the upper eyelets to the guide, and the lower row passes from the lower eyelets to the guide. The two rows intersect, or meet, at the guide to form an acute interior corner. This formation of two rows of threads is generally called a shed. Thus, a shed can basically be described as two flat planes, each formed by a row of parallel threads, which meet to form a trough, or corner.
To begin the weaving process a cross-thread, called a weft thread, is placed into the corner of the shed where the threads meet at the guide, and perpendicular to the warp threads. After placement of the weft thread, the position of each eyelet is reversed--that is, the upper eyelets move to the lower position, and the lower eyelets move to the upper position. This change in position of the eyelets not only forms another shed, but also causes the warp threads to partially wrap around the weft thread. A second weft thread is then inserted into the corner of the new shed, and the position of each eyelet is again reversed. This process is continually repeated to form a fabric created from interlacing, or weaving, the warp and weft threads.
Basic woven fabric is produced on weaving devices which move the eyelets in a continuously repeating sequence of shed changes to produce a homogeneous fabric pattern. However, special type of weaving device, called a Jacquard device, may be used, among other purposes, to weave intricate or varying patterns into the fabric, or to perform seaming operations wherein two edges of fabric are woven together.
Jacquard devices are also well known in the art and have been in existence for hundreds of years. In a Jacquard device, each eyelet is individually selectively movable with each shed change. In other words, the sequence of movements of the eyelets is not merely repetitive, but may vary with each shed change.
Generally speaking, a Jacquard weaving device consists of an array of springs mounted on the top end of the frame of the weaving device. An eyelet is attached to each of the springs and hangs from the lower end of the spring. The springs bias the eyelets toward an upper position. A pulley block is attached to the lower side of each eyelet and hangs below the eyelet. A cord is strung through the pulley block, engaging the sheave, or pulley wheel, and both ends of the cord hang below the pulley block. The cord has two hooks attached to it, one on each end, which hang below the pulley block.
Attached to the frame, are two parallel horizontal bars, called griff bars, which reciprocally move up and down below the pulley block. The griff bars ire mechanically linked together so that, as one griff bar moves up, the other correspondingly moves down, and vice versa. An actuator is coupled to one of the griff bars to reciprocally move the griff bars at continuously repeating intervals.
The hooks are both engaged to guides mounted on the frame which restrict the path of movement of the hooks such that the path of movement of one of the hooks coincides with that of one of the griff bars, and the path of movement of the other hook coincides that of the other griff bar. Each hook has a slot or similar means which is open at the top, such that as the respective griff bar moves downward, it engages the slot, capturing the respective hook and pulling it downward. If the hook is held in its lowest position, the upward facing slot on the hook allows the griff bar to disengage the hook and move upward while leaving the hook in its lower position.
The cord which is connected between the hooks is of such a length that the respective spring, located above the eyelet, keeps the cord taught at all times. When both hooks are engaged to each respective griff bar, the hooks and cord travel in a reciprocal see-saw motion along with the griff bars, with the cord being pulled back and forth through the pulley block and rolling over the sheave. During this see-saw motion, the pulley block and eyelet remain stationary in the upper position, being held up by the tension of the respective spring.
The lower end of each hook is engageable with a pair of latches which are mounted on the frame and are located near the bottom of the path of travel of the respective hook. Each latch selectively captures and retains the respective hook in the lower position. As previously mentioned, if one of the hooks is held in its lower position by the respective latch, the respective griff bar disengages the hook as it travels upward, leaving the hook retained by the latch in the lower position. As the first griff bar moves upward, leaving one of the hooks retained by the first latch, the second hook is simultaneously pulled downward toward the second latch by the second griff bar as the first griff bar travels upward. Because the first hook is latched in the lower position, and is not allowed to raise up as the second hook is being pulled downward, the pulley block is pulled downward by the cord attached between the hooks, which pulls the eyelet downward against the force of the respective spring. This results in the eyelet reaching a lower position as both hooks are in their respective lower positions.
For the eyelet to remain in the lower position, both the first and second hooks must be retained in their respective lower positions by their respective latches. In this manner, the griff bars continue to reciprocally move in a see-saw motion above both hooks, but do not cause movement of the hooks, cord, pulley block, or eyelet.
Conversely, for the eyelet to raise to its upper position once again, one of the latches must disengage its respective hook as the respective griff bar is in the lower position and engaged to the respective latch. In this manner, one of the hooks is released by the latch and allowed to raise up with the griff bar to its upper position under the tension of the spring. This results in the respective pulley block and eyelet moving upward to their respective upper positions. For the eyelet to remain in the upper position, the other latch must also release its respective hook, allowing the see-saw motion of the hooks and cord to resume as initially described.
Many Jacquard weaving devices utilize electric solenoids to cause the selective retention of the hooks by the latches. In this type of design, an electric solenoid is mounted on the frame near each respective latch. Mounted on each latch is a material, such as iron, which is attracted by the magnetic field produced by the solenoid when the solenoid is energized with electrical current. Generally, each latch is biased in a latched position. As a hook is moved into engagement with the respective latch, the hook pushes the latch into its unlatched position and toward the solenoid such that the magnetically attractable material is pressed against the solenoid. If the solenoid is energized, the material is held against the solenoid by the magnetic field, holding the latch in the unlatched position, which prevents the latch from retaining the hook in the lower position.
Conversely, if the solenoid is not energized, the bias of the latch causes the latch to move back to the latched position as the hook begins to move upward and disengage the latch. However, before the hook completely disengages the latch, the latch captures the hook, retaining it in the lower position. If the hook is retained by the latch, the subsequent downward stroke of the respective griff bar will again move the hook against the latch in a manner which will cause movement of the latch to the unlatched position. This enables the hook to be released from the latch if the latch is held in the unlatched position by the solenoid. In this manner, the weaving device selectively moves the eyelet by energizing and de-energizing the solenoids at given intervals which controls the movement of the hooks. Often a controller, such as a programmable logic computer, it utilized to selectively control electrical current flow to the solenoids, as well as the motion of the griff bars.
Commonly, a Jacquard weaving device consists of at least one row of eyelets which are configured as discussed above, with respective springs, pulley blocks, cords, hooks, latches and solenoids for each eyelet. Usually, the entire row of eyelets is served by a single pair of elongated griff bars. In this manner, each individual eyelet in the row may be moved from either the upper position to the lower position, or vice versa, or may remain in either the upper or lower position, with each reciprocal stroke of the griff bars. Often, large Jacquard weaving devices consist of several such rows of similarly configured eyelets, each with its own set of griff bars. Thus, by moving the griff bars at repeating intervals, and selectively controlling the energization of the solenoids, the controller can cause any combination of eyelets to either move up or down, or remain in the upper or lower positions, with each shed change.
While Jacquard weaving machines of conventional design have been operated with varying degrees of success, there have been associated shortcomings which have detracted from their usefulness. For example, a relatively large Jacquard weaving machine may consist of a dozen or more rows of eyelets, each row having up to thirty or more eyelets. Such a machine, having upwards of three hundred individually movable eyelets, will have a complex, tightly packed mechanism comprised of interactive, precision components, including griff bars and related drive trains, hooks, latches, solenoids, cords, guides, and pulley blocks. Thus, a malfunction or failure of a component in the center of this tightly packed mechanism necessitates a tedious and time-consuming disassembly task in order to simply gain access to the failed or malfunctioning part for removal and replacement. This tedious disassembly process of the machine results in costly down-time of the weaving device, during which the operation of the device is temporarily halted. Further, the solenoids sometimes fail to retain the respective latches due to misalignment of the latch a nd solenoid, causing a mis-weave.
Therefore, it has long been known that it would be desirable to provide a Jacquard weaving machine which achieves the benefits to be derived from similar prior art devices, but which avoids the detriments individually associated therefrom.